Indeed, there is truth in that old joke. In fact, Joseph R. Biden, Jr. has already had his ancestry researched by a number of researchers and it has been published on several web sites.
By the way, did you know Joe Biden’s middle name is Robinette? He inherited that name from his great-grandfather, George Hamilton Robinette (1844-1914), a Civil War veteran. It was also the middle name of the new President’s father.
Listings of Joe Biden’s ancestry are available all over the Internet. Two different sites caught my eye:
Family of Joe Biden on Wikipedia at https://en.wikipedia.org/wiki/Family_of_Joe_Biden provides a brief, but easy-to-read listing
Ancestry of Joe Biden by Rich Hall at https://famouskin.com/pedigree.php?name=48077+joe+biden&ahnum=1 provides a more detailed listing going back 10 generations in one line that will probably appeal to experienced genealogists.
My preference is the ahnentafel (list of ancestors) from Rich Hall’s listing:
Ancestry of Joe Biden
U.S. President-elect
Look → Click or tap a name to see more details including sources or famous kin.
1st Generation
1. Joseph Robinette Biden Jr. (1942–)
2nd Generation
2. Joseph Robinette Biden (1915–2002)
3. Catherine Eugenia “Jean” Finnegan (1917–2010)
3rd Generation
4. Joseph H. Biden (1893–1941)
5. Mary Elizabeth Robinette (c1894–1943)
6. Ambrose Joseph Finnegan (1883–1957)
7. Geraldine Catharine Blewitt (1886–1949)
4th Generation
8. George T. Biden (c1867–c1910)
9. Mary Emily Liddell (1872–1922)
10. George Hamilton Robinette (1844–1914)
11. Mary A. Hanafy (1862–1930)
12. James Finnegan (1840–c1895)
13. Catherine Roche (c1846–c1895)
14. Edward Francis Blewitt (1859–1926)
15. Mary Ellen Stanton (c1861–1888)
5th Generation
16. Joseph J. Biden (1828–1895)
17. Lydia Ann Randle (c1835–1902)
18. Robert Theodore Liddell (1844–1914)
19. Susan E. Bomberger (c1846–1924)
20. Moses J. Robinette (c1819–1903)
21. Jane E. Pumphrey (c1824–1878)
22. John Hanafy (1815–1878)
23. Mary —– (1828–1878)
24. Owen Finnegan (c1819–1875)
25. Jane Boyle (c1822–1874)
28. Patrick Blewitt (1832–1911)
29. Catharine Scanlon (c1838–1901)
30. James Stanton (c1831–)
31. Mary Arthurs (c1835–)
6th Generation
32. William Biden (c1800–)
33. Mary Elkins (c1801–)
34. Thomas H. Randle (c1803–1889)
35. Mary Ann Shoemaker (1813–1902)
36. John Liddell
37. Emily E. Wooben
38. John Bomberger (c1821–)
39. Mary —– (c1827–)
42. (probable) James Pumphrey (c1765–c1832)
43. (probable) Elizabeth Hamilton (–1820)
56. Edward Blewitt (c1805–c1870)
57. Mary Mulderig (c1803–c1860)
7th Generation
66. Joseph Elkins (1776–c1801)
67. Nancy Fonts
84. William Pumphrey (c1734–c1786)
85. Elizabeth Kingsbury (c1738–)
8th Generation
132. William Elkins (c1751–1798)
133. Mary Points (c1748–1798)
170. James Kingsbury
171. Anne Demilliane
9th Generation
340. James Kingsbury (–c1726)
341. Elizabeth Hall (c1673–c1743)
342. Gabriel Demilliane
343. Ann Young
10th Generation
682. Richard Hall (–c1688)
683. Elizabeth —– (–c1687)